1. Field of the Invention
The invention relates to a sampling circuit comprising a first main terminal and a series coupling of a hold capacitor and a sampling switch between said first main terminal and a second main terminal.
2. Description of the Related Art
The article "An improved correlated double sampling circuit for low-noise charge-coupled devices", IEEE transactions on circuits and systems, vol. 37, no. 12, december 1990, pp. 1559-1565 describes a prior an correlated double sampling circuit for low noise charge-coupled devices. The noise suppression of the circuit shown in FIG. 2 of the article is, however, not deemed to be good enough. The same holds for the improved circuit shown in FIG. 4 of the article, as in both circuits, the RC time constant of the low-pass filter preceding the proper correlated double sampling circuit cannot be large enough to obtain a good noise suppression, as a large RC time constant results in the disadvantage that the capacitors of the proper correlated double sampling circuit cannot be charged to their respective end values within the time slot between two sampling instants. If the time-constant of the low-pass filter preceding the correlated double sampling circuit, or any of the RC time constants of the proper correlated double sampling circuit, is large enough to obtain a satisfactory noise suppression, an undesired crosstalk between successive samples occurs.
The dual slope integration technique described in the overview article "Charge-coupled device signal processing models and comparisons", Journal of Electronic Imaging 2(2), 100-107 (April 1993), has a very good noise performance, but a circuit operating in accordance with the dual slope integration technique at sampling frequencies above 1 MHz, and certainly above 10 MHz, is difficult to manufacture. Consequently, dual slope integration cannot be applied to broadcast television cameras in which sampling rates of e.g., 36 MHz are used.